"Snowden is ready to return to the States, but on the condition that he is given a guarantee of a legal and impartial trial," Snowden's Russian lawyer Anatoly Kucherena said this week.

Ben Wizner, one of Snowden's American legal counsels, told U.S. News that Snowden should get leniency like General David Petraeus, the former CIA chief who this week agreed to serve two years probation and plead guilty to one misdemeanor.

"If Petraeus deserves exceptional treatment because of his service to the nation, then surely the same exception should be offered to Edward Snowden, whose actions have led to a historic global debate that will strengthen free societies," Wizner said.